A propane fireplace should be cleaned, at a minimum, every year. This includes all parts of the system from the intake valve and any grommets that may have aged to taking a stiff brush to make sure that all of the dirt is out of the propane system. At a year, it's also a good idea to replace any hoses that may be needed as they do take heavy use and are under pressure and cold. Finally, the bottle itself should be cleaned, paying special attention to the nozzle and shutoff valve, plus any relief valves that may be included. All parts should be replaced with new parts.